Hitler was certainly brilliant in certain ways, e.g. as a public speaker he must have been very persuasive. I don't think that changes anything about how utterly insane his (and his fellow Nazis') ideology was, though.

There are "effective" dictators who manage to have a stable, if brutal reign, and then there's Nazi-ism which at its very core is such a destructive ideology that it can't really even sustain itself in the long run.